Glucose production from glycogen by gluconeogenesis and glycogenolysis is a vital function of the liver and to a lesser extent, the kidney cortex during starvation. Both processes result in the formation of glucose-6-phosphatase (G6P). The glucose-6-phosphatase (G6Pase) system regulates the dephosphorylation of glucose-6-phosphatase to glucose thereby playing a critical role in glucose homeostasis (van Schaftingen and Gerin, Biochem. J., 362, 513-532).
G6Pase deficiency results in glycogen storage disease, also known as van Gierke disease, primarily resulting in hypoglycemia. The G6Pase protein system is composed of at least a catalase (G6PC1) and a translocase (G6PT1). Defects in G6PC1 are associated with glycogen storage disease type I (GSD I, later referred to as GSD Ia) and defects in G6PT1 are associated with a variant of GSD I referred to as GSD Ib (van Schaftingen and Gerin, Biochem. J., 362, 513-532).
GSD Ib, although less prevalent than GSD Ia, presents a panoply of maladies. At infancy, GSD type Ib patients exhibit a failure to thrive, hypoglycemia-induced seizures, hepatomegaly, recurrent bacterial infections, anemia and acute lactic acidosis. Dietary management of the disease in children requires continuous nighttime feedings by nasogastric or gastrostomy tube and by dietary regimens that include regular drinks of uncooked starch. As the children age, metabolic complications subside and the disease is more easily managed by frequent daytime meals. GSD Ib is clinically distinguishable from GSD Ia because GSD Ib patients frequently have neutropenia and/or neutrophil dysfunction rendering them more susceptible to bacterial infections, typically involving the skin, perirectal area, ears, and urinary tract. Gingivitis and mouth ulceration are common, and chronic inflammatory bowel disease does occur. Hyperlipidemia and hyperuricemia frequently occurs and require treatment as the patients age. With advancing years hepatoma, renal disease, gout and osteoporosis become more likely. Annual ultrasound or computed tomographic scans are indicated for patients over 20 years of age (Kannourakis, Semin. Hematol., 39, 103-106).
GSD Ib patients exhibit similar clinical symptoms to GSD Ia patients, yet unlike GSD Ia patients, the livers from GSD Ib patients possess normal or increased glucose-6-phosphatase activity in detergent-disrupted microsome preparations. In contrast, such enzymatic activity was absent or reduced in intact microsomes. (An et al., J. Biol. Chem., 276, 10722-10729) The identification of the G6PT1 cDNA confirmed that the disease was a result of deficient glucose-6-phosphatase transport rather than deficient catalytic activity.
The G6PT1 cDNA (also known as G6P translocase, glucose-6-phosphatase translocase, glucose-6-phosphatase, transport protein 1, glucose-6-phosphatase transporter 1, glycogen storage disease type 1b, GSD type Ib, GSD1b, MGC15729, and PRO0685) was isolated and found to be mutated in two patients with GSD type Ib (Gerin et al., FEBS Lett., 419, 235-238; Veiga-da-Cunha et al., Am. J. Hum. Genet., 63, 976-983). The gene was mapped to chromosome 11q23 (Veiga-da-Cunha et al., Am. J. Hum. Genet., 63, 976-983). Homologous cDNA clones were isolated from the mouse and rat (Lin et al., J. Biol. Chem., 273, 31656-31660).
The human G6PT1 gene contains nine exons. Exon 7 is absent in human liver and leukocyte RNA but present in heart and brain. The alternatively spliced products retain the reading frame. Also, there are two transcription start sites at approximately −200 and −100 relative to the initiator ATG (Gerin et al., Gene, 227, 189-195). G6PT1 expression increased 2-3 fold in insulin-deficient streptozocin-induced diabetes in liver, kidney and intestine of rats. Increased glucose concentrations increased G6PT1 mRNA levels while increased cAMP concentrations decreased G6PT1 mRNA levels. Consequently, these results indicate that G6PT1, as well as the catalytic subunit, is impaired in insulin-dependent diabetes (Li et al., J. Biol. Chem., 274, 33866-33868). Similarly, treatment of hyperglycemic rats with an inhibitor of G6PT1, a chlorogenic acid derivative, suppressed blood glucose levels (Herling et al., Eur. J. Pharmacol., 386, 75-82). Furthermore, treatment of rats with a chlorogenic acid derivative increased de novo lipogenesis and steatosis but left VLDL-triglyceride secretion unaffected (Bandsma et al., Diabetes, 50, 2591-2597). Unfortunately, while these properties make chlorogenic acid derivatives promising candidates as drugs for the treatment of type II diabetes, such compounds exhibit a short duration of action due to high plasma clearance and rapid elimination into the bile (Herling et al., Biochim. Biophys. Acta, 1569, 105-110).
As a consequence of G6PT1 involvement in diabetes and glycogen storage disease, there remains a long felt need for agents capable of effectively regulating G6PT1 function.
Antisense technology is emerging as an effective means for reducing the expression of specific gene products and has been proven to be uniquely useful in a number of therapeutic, diagnostic, and research applications.
Disclosed herein are antisense compounds useful for modulating gene expression and associated pathways via antisense mechanisms of action such as RNaseH, RNAi and dsRNA enzymes, as well as other antisense mechanisms based on target degradation or target occupancy. One having skill in the art, once armed with this disclosure will be able, without undue experimentation, to identify, prepare and exploit antisense compounds for these uses.